There have previously been proposals for headlights which comprise a light source mounted in a reflector which is adapted to be tilted selectively between a first position and a second position. In the first position the light produces a beam which extends laterally a passing or dipped beam which is produced in parallel by a dedicated dipped beam headlight. In the second position, the headlight produces a beam which is suitably adapted for use in fog.
However, for various reasons, especially selling cost and reliability, it is in general preferred that headlights be defined in which the reflectors occupy a fixed position (apart of course from the facility for adjusting the horizontal and azimuth positions of the headlight during fitting or in operation in order to compensate for attitude variations of the vehicle). It will however be understood that recourse to such a fixed reflector is incompatible with known proposals for headlights combining the turning beam and foglight functions. 
In addition, in the above mentioned headlights with tilting reflectors, having a common cover lens, it can be a somewhat difficult matter to design the reflector in such a way that it will produce both a satisfactory turning beam and a satisfactory beam for use in fog.